Combines are well known in the art. They are available in various designs and models to perform the basic functioning of harvesting, threshing, and cleaning of grain. As used herein, the term "grain" is meant to include corn, wheat, rye, oats, barley, flax seed, sorghum, soy beans, mixed grain, and any other food grains, feed grains, and oil seeds.
A typical combine includes a crop harvesting apparatus which reaps planted grain stalks. An infeed mechanism arranged at a forward end of the combine operates in combination with the harvesting apparatus and feeds the grain stalks through a separating apparatus. The separating apparatus threshes and separates the grain from material other than grain.
While the separating apparatus acts to separate a substantial portion of the crop or grain from material other than grain, some chaff and/or straw remains intermixed with the grain and a further cleaning or separating action is normally required. Further separation is normally achieved in a cleaning section of the combine.
The cleaning section of a conventional combine receives grain and other material expelled from the separating apparatus. A typical cleaning section includes two reciprocally mounted sieves and a fan which produces a flow of air directed toward the sieves. Reciprocation of the sieves facilitates arrangement of the grain and other materials into a crop layer or mat on top of the sieves. Each sieve preferably includes a series of adjacent louvers or slats. A series of openings or passages is defined between adjacent slats to grade the material by size such that smaller granular particles are allowed to fall through the openings but causing larger pieces of material such as straw, chaff, and the like to be moved rearwardly and off the sieves. The material moved off the sieves is returned to the separating apparatus for rethreshing.
Separation of the crop material is facilitated by a forced flow of air created by the fan and flowing upwardly through the passages between the slats on the sieves. The upwardly directed air creates a force which urges residue material including straw, chaff, and the like to float on top of the sieves and into an airborne state such that it may be directed toward and expelled from a discharge end of the combine. The heavier seeds or clean grain tend to move to the sieve and fall through the openings or passages into a clean grain collector.
As long as the combine is operated on a generally level ground contour, heretofore known cleaning systems offer an efficient and effective separation of the crop material. Operational efficiency is adversely affected, however, when the combine or harvester is operated on a lateral incline or hillside. When a combine is operated on a hillside, there is a substantial loss of grain because the crop material received from the separating apparatus moves to the downhill side of the sieves. The crop materials build up to such a depth that the separating or cleaning function is substantially impaired or crop material spills over the downhill side of the cleaning sieves.
Conventional cleaning sieves have no means of maintaining an even layer or mat of crop material over the cleaning surface thereof. Thus, when the combine is operated on the hillside, crop material wants to move downhill with operation or reciprocation of the sieves. The crop material builds up or banks along the lower edge of the sieves to such a depth that the air flow from the fan is unable to penetrate and separate the grain from material other than grain. As will be understood, the air tends to follow the path of least resistance and blows through an uphill side of the cleaning sieve whereat it is insufficient to separate the crop material. As a result, the crop material proceeds rearwardly and falls off the edge of the sieve and it is discharged from the rear end of the combine. Grain loss can be quite excessive in these conditions.
There are combines which are specifically designed to operate on hillsides. Such combines are typically provided with hydraulic leveling devices that permit the harvesting apparatus to remain tilted according to the hillside slope while the cab region and grain cleaning assembly are adjustably rotated about a fore-and-aft axis and remain fairly level. Thus, among other things, the crop material received onto the sieves for separation and cleaning is spread out fairly evenly such that the cleaning action can be carried out relatively efficiently. Such selectively tiltable, hydraulic leveling systems, however, are quite expensive and thus are financially beyond the reach of many who would perhaps seriously be in need of such features. Moreover, the majority of combines which are sold are the "level land" type which suffer the loss grain problems discussed in detail above when operated on a hillside.
Additional efforts have been made to devise attachments which would effectively prevent crop material from accumulating on one side or the other of the sieves. One such attempt involves the attachment of structural members or dividers which are transversely spaced apart and extend fore-and-aft along a portion of and above the sieves. During inclined combine operation, the crop material moves downwardly toward the divider and forms an increasingly deeper mat which extends up to level with the top surface of the divider. As material depth exceeds the height of the divider, it flows thereover and moves further downhill. As will be appreciated, the crop material mat is quite deep near the divider while very little crop material is distributed over an uphill portion of the cleaning sieves.
Thus, there is a need and a desire for a cleaning system which facilitates distribution of grain and material other than grain over a broad cleaning area when the combine is tilted during slope harvesting.